Radio Frequency Identification Tagging

ABSTRACT

A Radio Frequency Identification (RFID) tag has an electronic identification circuit coupled to an antenna, wherein the RFID tag is arranged to communicate with a RFID tag reader via the antenna, using RF energy. The tag comprises means sensitive to light (such as a photodiode, phototransistor, photocell or a solar cell) for controlling (in particular inhibiting) communication between the RFID tag reader and the RFm tag. The tag can for example be embedded in or on a high-value object such as a banknote. The existence of the banknote cannot be detected e.g. by criminals in the absence of light (e.g. while the banknote is located in a wallet), but the authenticity of the banknote can be verified in legitimate use.

The present invention relates to a Radio Frequency Identification (RFID)tag and a use of such a RFID tag.

RFID tags are currently in widespread use, inter alia as securityfeatures. There are proposals to equip banknotes, credit cards, debitcards, store loyalty cards and other high-value objects with RFID tagsin an attempt to prevent fraud.

The present inventor has appreciated that there may be privacy andsecurity concerns if the objects listed above (in the following referredto as high-value objects) are equipped with a RFID tag. For example,whilst embedding a RFID tag in a banknote would enable the identity andauthenticity of the banknote to be verified by a suitable RFID reader,it might also enable a criminal who is in the possession of a suitableRFID reader to detect whether a particular person is carrying a largeamount of money. This would, of course, be undesirable.

The present invention has been made to address this concern.

Aspects of the present invention are set out in the independent claims.

In one aspect the present invention provides a Radio FrequencyIdentification (RFID) tag comprising:

-   -   an electronic identification circuit coupled to an antenna,        wherein the RFID tag is arranged to communicate with a RFID tag        reader via said antenna, using RF energy, and    -   means sensitive to light for inhibiting communication between        the RFID tag reader and the RFID tag.

The means sensitive to light (for example a photodiode, aphototransistor, a photocell or a solar cell) can ensure that the RFIDtag can only be read when exposed to (sufficient) light, for exampleambient light. Conversely, when the RFID tag is not exposed to(sufficient) light, e.g. if the tag is embedded in a banknote and thebanknote is placed in a wallet, the RFID tag cannot be read by a RFIDreader.

The electronic identification circuit may be powered by RF energyreceived via the antenna, or alternatively it may be powered by a sourceof energy other than the antenna, for example a battery. Preferably, themeans sensitive to light is arranged to reduce the range over which saidRFID tag can transmit information to said reader in the absence of lightof more than a predetermined threshold. Such an arrangement can be ofuse if it is desired to enable legitimate use of a high-value objectdespite the absence of light when the high-value object is brought intoclose proximity to a RFID tag reader. For example, it may be desirablefor a credit card carrying the tag to be used for payment even if thecredit card remains in a wallet. The tag could be configured such thatit can be read (even in the absence of light) over a distance of a fewmillimetres or centimetres. Detection of the credit card by criminalscould still be prevented as they are less likely to be able to bring aRFID tag reader into such close proximity to a potential victim'swallet.

In a second aspect, and as an inventive extension of the first aspect,the present invention provides a Radio Frequency Identification (RFID)tag comprising:

-   -   an electronic identification circuit coupled to an antenna,        wherein the RFID tag is arranged to communicate with a RFID tag        reader via said antenna, using RF energy, and    -   means sensitive to light for controlling communication between        the RFID tag reader and the RFID tag.

The inventor has recognised that the means sensitive to light caninfluence the operation of the RFID tag in various ways. For example,the means sensitive to light could solely, mainly or partly beresponsible for supplying the energy necessary for communication betweenthe RFID tag and the RFID tag reader.

Preferably, the electronic identification circuit is powered by energyreceived from the means sensitive to light when the means sensitive tolight is exposed to substantially continuous, ambient light, for examplenormal daylight or room lighting.

Some preferred embodiments of the invention will now be described by wayof example only and with reference to the accompanying drawings, inwhich:

FIG. 1 shows a simplified circuit diagram of a RFID tag according to afirst embodiment of the present invention;

FIG. 2 shows a simplified circuit diagram of a RFID tag according to asecond embodiment of the present invention; and

FIG. 3 shows a use of a tag according to the present invention.

FIG. 1 shows an electronic identification circuit 10 having (in theexample shown eight) pin connectors 15. Two of these are connected atpoints 25 and 35 respectively to a power source (not shown) generating avoltage V_(CC)-V₀ between lines 20 and 30. Line 20 is connected to line30 via resistor 50 arranged in series with light sensitive element 40.The potential between resistor 50 and light sensitive element 40 isapplied to one of the pin connectors 15 at point 45. The otherconnections of pin connectors 15 are not shown. At least one antenna(shown only in FIG. 2 at 11 and 12) is coupled to the electronicidentification circuit 10 for communicating with a RFID tag reader usingRF energy.

Instead of a separate power source, the antenna (driven by RF energyreceived from the tag reader) may be used to provide power for the RFIDtag. The tag could also have two antennas, one for communication withthe tag reader and one for providing power for the tag.

The electronic identification circuit 10 is set up such thatcommunication with a RFID tag reader is disabled if the potential atpoint 45 is sufficiently close to V_(CC). If the potential at point 45is close to V₀ then the electronic identification circuit 10 is enabledfor communication with the RFID tag reader.

The light sensitive element 40 can for example be selected from aphotodiode, a phototransistor, a photocell or a solar cell. Theconnection shown in FIG. 1 is particularly suitable for a photodiode,but other light sensitive elements can be used, and any necessarymodifications to the circuit diagram will be clear to one skilled in theart enlightened by the present disclosure. For the purpose of thefollowing description of the first embodiment it will be assumed thatthe light sensitive element 40 comprises a photodiode.

In operation, in the absence of light the resistance of photodiode 40will be much larger than in the presence of light. Assuming thatsuitable resistance values are chosen for the resistor 50 (which couldbe a standard ohmic resistor), the resistance of the photodiode 40 willbe much lower than the resistance of the resistor 50 in the presence oflight, and the resistance of the photodiode 40 will be much larger thanthe resistance of the resistor 50 in the absence of light. This meansthat in the presence of light the potential at point 45 is close to V₀,whereas in the absence of light it will be close to V_(CC). Theelectronic identification circuit 10 is configured such that a potentialclose to V_(CC) at point 45 will disable the circuit as regardscommunication with the tag reader. The signal on point 45 can hence beconsidered as a disabling signal.

As an alternative, the position of photodiode 40 and resistor 50 couldbe swapped and the circuit 10 set up such that it can only communicatewith the tag reader if the potential at point 45 is close to V_(CC).

FIG. 2 shows a second embodiment comprising an electronic identificationcircuit 10 coupled to an antenna 11, 12 and connected at points 25 and35 to a solar cell 40 (as a representative example of a light sensitiveelement). The solar cell 40 powers the circuit 10, which means that inthe absence of light (assuming the circuit 10 is not powered by othermeans) the circuit is disabled, i.e. cannot communicate with a RFID tagreader. A diode and/or rectifier (not shown) may be required in theconnection between the solar cell 40 and the electronic identificationcircuit 10. The diode and/or rectifier can be integrated into thecircuit 10.

Whilst the light sensitive element 40 of the first embodiment merely hasthe function of generating a disabling/enabling signal, the lightsensitive element 40 of the second embodiment has to provide the powerfor the RFID tag.

As a third embodiment (a modification of the second embodiment), theelectronic identification circuit 10 can be set up such that the RFenergy received by the antenna 11, 12 from a suitable RFID tag reader isused to power the circuit 10, i.e. to provide the energy necessary forre-transmitting a signal back to the RFID tag reader. This could forexample be sufficient to enable the tag to be read over a distance of afew millimetres or centimetres. Since the circuit is also powered bysolar cell 40 the range over which the tag can be read is increased inthe presence of light.

The arrangement shown in FIG. 2 is suitable for use in the thirdembodiment. However, as compared with the second embodiment, additionaldiodes and/or rectifiers (not shown) may need to be used to connect thesolar cell and the antenna to the identification circuit so as to ensurethat both can be used to power the RFID tag. Again, these diodes and/orrectifiers can be integrated into the circuit 10. It will be clear toone of ordinary skill in the art how any such diodes and/or rectifierswould need to be connected.

According to the first and second embodiments, in the absence of lightthe tag cannot be read by a RFID tag reader at all. By way of contrast,according to the third embodiment the RFID tag can be read at all times,but the range over which the tag can be read is increased in thepresence of light.

FIG. 3 shows schematically an example of application for the abovedescribed technique. Shown in FIG. 3 is a high value object 60 (such asa credit card, debit card, store loyalty card or banknote) in which oron which is arranged a tag according to the first, second or thirdembodiment. This tag is schematically shown as RFID identificationcircuit 10 connected to light sensitive element 40. Other details havebeen omitted for simplicity.

Although the invention has been described in terms of preferredembodiments as set forth above, it should be understood that theseembodiments are illustrative only and that the claims are not limited tothose embodiments. Those skilled in the art will be able to makemodifications and alternatives in view of the disclosure which arecontemplated as falling within the scope of the appended claims. Eachfeature disclosed or illustrated in the present specification may beincorporated in the invention, whether alone or in any appropriatecombination with any other feature disclosed or illustrated herein.

1. A Radio Frequency Identification (RFID) tag comprising: an electronicidentification circuit coupled to an antenna, wherein the RFID tag isarranged to communicate with a RFID tag reader via said antenna, usingRF energy, and means sensitive to light for inhibiting communicationbetween the RFID tag reader and the RFID tag.
 2. A RFID tag according toclaim 1, wherein the electronic identification circuit is powered by RFenergy received via said antenna or via a further antenna.
 3. A RFID tagaccording to claim 1, wherein the electronic identification circuit ispowered by a source of energy other than said antenna.
 4. A RFID tagaccording to claim 1, wherein the means sensitive to light is arrangedto substantially prevent information to be transmitted from said RFIDtag to said reader in the absence of light of more than a predeterminedthreshold.
 5. A RFID tag according to claim 1, wherein the meanssensitive to light is arranged to reduce the range over which said RFIDtag can transmit information to said reader in the absence of light ofmore than a predetermined threshold.
 6. A RFID tag according to claim 1,wherein the means sensitive to light is selected from one of aphotodiode, a phototransistor, a photocell or a solar cell.
 7. Ahigh-value object including a RFID tag according to claim
 1. 8. Use of aRFID tag according to claim 1 to tag a high-value object.
 9. Ahigh-value object according to claim 7, wherein the high-value object isselected from a banknote and a credit card.
 10. A RFID tag according toclaim 1, wherein the means sensitive to light is arranged to inhibitsaid communication when exposed to ambient light.
 11. A Radio FrequencyIdentification (RFID) tag comprising: an electronic identificationcircuit coupled to an antenna, wherein the RFID tag is arranged tocommunicate with a RFID tag reader via said antenna, using RF energy,and means sensitive to light for controlling communication between theRFID tag reader and the RFID tag.
 12. A RFID tag according to claim 11,wherein the electronic identification circuit is powered by energyreceived from said means sensitive to light when said means sensitive tolight is exposed to substantially continuous, ambient light.
 13. A RFIDtag according to claim 1, wherein the means sensitive to light issensitive to visible light irrespective of the frequency of that light.14. (canceled)